Higher oxidation states of prostaglandin H synthase

Dietz, Reiner; Nastainczyk, Wolfgang; Ruf, Hans Heinrich

doi:10.1111/j.1432-1033.1988.tb13793.x

Cited by 233 publications

(240 citation statements)

References 20 publications

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“…Mutation of Gly-533 at the top of this channel seals off the channel and abolishes the oxygenation of arachidonic acid but not that of fatty acids with shorter carbon chains. 33 Ruf and co-workers 34 first proposed a mechanism that included the requirement of peroxide-dependent heme oxidation to initiate a mechanistically coupled oxygenase reaction in the spatially separate cyclooxygenase active site in the protein. In this mechanism (Figure 6), a hydroperoxide reacts with the heme iron to effect a two-electron oxidation to yield compound I (an oxyferrylheme radical cation), which rapidly carries out an intramolecular electron transfer from Tyr-385 to the heme to form a tyrosyl radical at position 385 (intermediate I).…”

Section: Cyclooxygenase Enzymes: Structure and Mechanismsmentioning

confidence: 99%

Structural and Functional Basis of Cyclooxygenase Inhibition

2007

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Section: Cyclooxygenase Enzymes: Structure and Mechanismsmentioning

confidence: 99%

Structural and Functional Basis of Cyclooxygenase Inhibition

2007

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“…Earlier analyses of PGHS-1 peroxidase kinetics relied primarily on rapid-scan stopped-flow measurements (3,4,11). Tyrosyl radical kinetic studies using rapid-freeze quench and EPR methods were conducted primarily with convenient, water soluble peroxides such as EtOOH (12), and more physiologically relevant lipid peroxides have not been investigated in detail.…”

Section: Introductionmentioning

confidence: 99%

“…Intermediate II is the starting point for peroxide-induced peroxidase inactivation (9). However, it remains unclear which of the two oxidants generated after reaction with peroxide, the oxyferryl heme or the tyrosyl radical, is the damaging species.Earlier analyses of PGHS-1 peroxidase kinetics relied primarily on rapid-scan stopped-flow measurements (3,4,11). Tyrosyl radical kinetic studies using rapid-freeze quench and EPR methods were conducted primarily with convenient, water soluble peroxides such as EtOOH (12), and more physiologically relevant lipid peroxides have not been investigated in detail.…”

mentioning

confidence: 99%

“…An intramolecular electron transfer converts Intermediate I to Intermediate II, which contains two oxidants: oxyferryl heme, or Compound II, in the peroxidase site and a tyrosyl radical on residue 385 in the cyclooxygenase channel (3)(4)(5). The Tyr385 radical abstracts the pro-S hydrogen atom from C13 of AA, initiating cyclooxygenase catalysis and PGG 2 formation (6).…”

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Oxyferryl Heme and Not Tyrosyl Radical Is the Likely Culprit in Prostaglandin H Synthase-1 Peroxidase Inactivation

Rogge

Wang

et al. 2006

Biochemistry

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Prostaglandin H synthase-1 (PGHS-1) is a bifunctional heme protein catalyzing both a peroxidase reaction, in which peroxides are converted to alcohols, and a cyclooxygenase reaction, in which arachidonic acid is converted into prostaglandin G 2 . Reaction of PGHS-1 with peroxide forms Intermediate I, which has an oxyferryl heme and a porphyrin radical. An intramolecular electron transfer from Tyr385 to Intermediate I forms Intermediate II, which contains two oxidants: an oxyferryl heme and the Tyr385 radical required for cyclooxygenase catalysis. Self-inactivation of the peroxidase begins with Intermediate II, but it has been unclear which of the two oxidants is involved. The kinetics of tyrosyl radical, oxyferryl heme, and peroxidase inactivation were examined in reactions of PGHS-1 reconstituted with heme or mangano protoporphyrin IX with a lipid hydroperoxide, 15-hydroperoxyeicosatetraenoic acid (15-HPETE), and ethyl hydrogen peroxide (EtOOH). Tyrosyl radical formation was significantly faster with 15-HPETE than with EtOOH and roughly paralleled oxyferryl heme formation at low peroxide levels. However, the oxyferryl heme intensity decayed much more rapidly than the tyrosyl radical intensity at high peroxide levels. The rates of reactions for PGHS-1 reconstituted with MnPPIX were approximately an order of magnitude slower, and the initial species formed displayed a wide singlet (WS) radical, rather than the wide doublet radical observed with PGHS-1 reconstituted with heme. Inactivation of the peroxidase activity during the reaction of PGHS-1 with EtOOH or 15-HPETE correlated with oxyferryl heme decay, but not with changes in tyrosyl radical intensity or EPR line shape, indicating that the oxyferryl heme, and not the tyrosyl radical, is responsible for the self-destructive peroxidase side reactions. Computer modeling to a minimal mechanism was consistent with oxyferryl heme being the source of peroxidase inactivation.Prostagladin H synthases (PGHSs) catalyze the first two steps in biosynthesis of prostaglandins, the cyclooxygenase reaction that converts arachidonic acid (AA) 1 to prostaglandin (PG)G 2 and the peroxidase reaction that reduces PGG 2 to PGH 2 (1). The cyclooxygenase reaction is dependent upon formation of the Tyr385 radical during the peroxidase reaction (2). A simplified mechanistic model is shown in Figure 1. According to † This work was supported by U.S. Public Health Service Grants GM44911 (to A.-L.T.), GM52170 (to R.J.K.), and GM55807 (to G.P.) and Postdoctoral Fellowship DK61929 (to C.E.R.), and Welch Foundation Grant C636 (to G.P. Reaction with peroxide drives the redox events that lead to strong feedback amplification of cyclooxygenase catalysis, and it also drives the irreversible self-inactivation of both peroxidase and cyclooxygenase activities that imposes an upper limit on prostanoid synthesis (7,8).Cyclooxygenase inactivation induced by peroxide occurs on the same time scale as peroxidase inactivation, although the former seems more sensitive to the peroxide structure (9,1...

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“…Their potential cardioprotective role is discussed. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]AA (51 mCi/mmol), Sephadex G-25, and Tween 20 were purchased from Sigma. PGF 2␣ , PGE 2 , and PGD 2 were purchased from Biomol Research Laboratories.…”

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Resveratrol is a Peroxidase-mediated Inactivator of COX-1 but Not COX-2

Szewczuk

Forti

Stivala

et al. 2004

Journal of Biological Chemistry

212

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Resveratrol (3,4 ,5-trihydroxy-trans-stilbene) is a phytoalexin found in grapes that has anti-inflammatory, cardiovascular protective, and cancer chemopreventive properties. It has been shown to target prostaglandin H 2 synthase (COX)-1 and COX-2, which catalyze the first committed step in the synthesis of prostaglandins via sequential cyclooxygenase and peroxidase reactions. Resveratrol discriminates between both COX isoforms. It is a potent inhibitor of both catalytic activities of COX-1, the desired drug target for the prevention of cardiovascular disease, but only a weak inhibitor of the peroxidase activity of COX-2, the isoform target for nonsteroidal anti-inflammatory drugs. We have investigated the unique inhibitory properties of resveratrol. We find that it is a potent peroxidase-mediated mechanism-based inactivator of COX-1 only (k inact ‫؍‬ 0.069 ؎ 0.004 s ؊1 , K i(inact) ‫؍‬ 1.52 ؎ 0.15 M), with a calculated partition ratio of 22. Inactivation of COX-1 was time-and concentration-dependent, it had an absolute requirement for a peroxide substrate, and it was accompanied by a concomitant oxidation of resveratrol. Resveratrolinactivated COX-1 was devoid of both the cyclooxygenase and peroxidase activities, neither of which could be restored upon gel-filtration chromatography. Inactivation of COX-1 by [ 3 H]resveratrol was not accompanied by stable covalent modification as evident by both SDS-PAGE and reverse phase-high performance liquid chromatography analysis. Structure activity relationships on methoxy-resveratrol analogs showed that the m-hydroquinone moiety was essential for irreversible inactivation of COX-1. We propose that resveratrol inactivates COX-1 by a "hit-and-run" mechanism, and offers a basis for the design of selective COX-1 inactivators that work through a mechanism-based event at the peroxidase active site.

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Higher oxidation states of prostaglandin H synthase

Cited by 233 publications

References 20 publications

Structural and Functional Basis of Cyclooxygenase Inhibition

Structural and Functional Basis of Cyclooxygenase Inhibition

Oxyferryl Heme and Not Tyrosyl Radical Is the Likely Culprit in Prostaglandin H Synthase-1 Peroxidase Inactivation

Resveratrol is a Peroxidase-mediated Inactivator of COX-1 but Not COX-2

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